This short video shows the movements of three main types of soil protozoa photographed at 1000X magnification.

Soil protozoa are small, single-celled, eukaryotic organisms that are part of the soil food chain. They consume smaller organisms, mainly bacteria, and smaller pieces of organic debris. They are heterotrophic and use the carbon contained in their food to build their own bodies and as an energy source. During this process, they multiply by asexually reproduction (splitting) and respire carbon dioxide back into the atmosphere. Other organisms such as rotifers and nematodes use protozoa as a food source. As eukaryotic organisms, they possess membrane-bound organelles and nuclei. They are classified by how they move: the ciliates have small hairs on their surface that beat in unison, the flagellates usually have two-to-four long whip-like structures called flagella, and the amoebae move by extruding their protoplasm in the direction of movement (the plastic nature of the moving protoplasm is called pseudopodia or false feet). Most are too small to be seen by the naked eye and commonly range in size from 10 to 50 µm, although some are smaller and others larger (the ciliates tend to be larger and the flagellates smaller). Numbers in a fertile soil often are in the thousands to hundreds of thousands per gram.

Organisms were grown on cornmeal extract agar using the procedures found in Loynachan (2006). Magnification of all images was at 1000X.

Amador, J.A., and J.H. Gorres. 2005. Fauna. pp. 181-200. In: D.M. Sylvia et al. (ed.) Principles and Applications of Soil Microbiology (2nd ed), Prentice Hall, Upper Saddle River, NJ.

Coleman, D.C., and D.H. Wall. 2015. Soil fauna: Occurence, biodiversity, and roles in ecosystem function. pp. 111-149. In: E.A. Paul (ed.) Soil Microbiology, Ecology, and Biochemistry (4th ed), Elsevier, New York, NY.

Loynachan, T. E. 2006. Quick, easy method to show living soil organisms to high school or beginning-level college students. J. Nat. Res Life Sci. Ed. 35:202-208.